Method for making an olefin-free high-octane fuel



Nov. 12, 1968 FEED FEED

FEED

Filed May 13, 1966 METHOD FOR MAKING AN OLEFIN-FREE, HIGH-OCTANE FUEL HF ALKYLATION paoouca' F/G.

a lo N I? k HF ALKYLATION W9 is :4 13 SOLVENT EXTRACTION j PRODUCTY FIG. 2

'C4HIO] nz' V 22 TH? ALKYLATION' 21 I7' (le' 24 25 I4 I 23 SOLVENT 1e 2e EXTRACTION PRODUCTJ FIG 3 INVENTOR L. E. DREHMAN United States Patent 3,410,788 METHOD FOR MAKING AN OLEFIN-FREE HIGH-OCTANE FUEL Lewis E. Drehman, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed May 13, 1966, Ser. No. 549,926 7 Claims. (Cl. 208-87) ABSTRACT OF THE DISCLOSURE An olefin-free, high-octane gasoline or motor fuel of reduced sensitivity is produced by fractionating a substantially full range catalytically cracked gasOline into at least two fractions, in one form of the invention a fraction boil-ing substantially below about 175 F .and another boiling substantially above 175 F., solvent extracting the higher boiling fraction to obtain a rafiinate substantially freed from aromatics and an extract containing aromatics substantially free from olefins, paraffins, and naphthenics. Alkylating in presence of each other, the raffinate and fraction boiling below about 175 F. and combining alkylate thus produced with said extract. In one modification of the invention prior to combining the alkylate and extract fractions, the alkylate is fractionated to produce at least two fractions, a fraction in one embodiment boiling below about 275 F. and one boiling above about 275 F., the latter being subject to aromatizing conditions following which the stream boiling below about 275 F., the aromatized stream and the extract stream are combined.

This invention relates to the preparation of motor fuels. More specifically, it relates to the preparation of an olefin-free, high octane gasoline or motor fuel of reduced sensitivity.

A concept of the invention accomplishes the reduction of sensitivity of the fuel (Research Octane Number=Motor Octane Number, both with 3 ml. of TEL) and lower olefin content of the fuel, which is prepared from a substantially full range catalytically cracked gasoline, containing substantial proportions of paraflins, olefins, cyclics and aromatics, by (A) fractioning the fuel into essentially at least two fractions (1) a fraction boiling substantially below a selected temperature, e.g., about 175 F., and (2) a fraction boiling substantially above said selected temperature (B) solvent extracting the latter, obtaining a substantially aromatics-free raflinate and an extract containing aromatics substantially free from olefins, parafiins and cyclics, e.g., naphthenics (C) subjecting the raflinate together with the fraction boiling below 175 F. to alkylation conditions, as desired, with added isoparaffin, and (D) combining the alkylate, thus obtained, suitably, with said extract.

Another concept of the invention further improves the catalytically cracked gasoline starting material by (C fractionating at least a portion of said alkylated product into essentially at least two fractions (e) a fraction boling below a selected temperature,

e.g., about 275 F., and (f) a fraction boiling above said selected temperature (C subjecting the latter fraction to conditions converting parafiins therein substantially to aromatics and then (D combining suitably the last obtained aromatics product, the fraction boiling below 275 F. and said extract.

I have conceived a combination of steps and a Patented Nov. 12, 1968 modification thereof with further steps which, applied to a catalytically cracked gasoline, will produce a sub stantially olefin-free gasoline of high octane number. The advantages of such an improved gasoline and, therefore, of the steps to produce the same are evident to one skilled in the art. Notably, reduction of olefin content of fuels, it appears, will become increasingly important as smog prevention is further regulated by government. Also, the increased octane number required for engines is served by the invention in its several concepts.

The individual reactions and the several steps of the combinations of the invention, as well as their conditions, are generally well known in the art. The present concepts are of combinations of steps resulting in so subdividing the original gasoline that solvent extracting of a suitable fraction can be practiced, in solvent extracting said fraction and in combining suitable fractions for the alkylation, followed by the suitable combining of the resultant products and the extract fraction, in the first concept set out above, that a much improved gasoline or fuel is ob tained, and, in so subdividing the alkylated product obtained and in practicing the conversion on a fraction thereof, that suitably even a much more improved gasoline is obtained when practicing the second concept set out above.

It is an object of the invention to produce an improved fuel. It is another object of the invention to produce an improved high-octane gasoline which is substantially olefin free by suitably analyzing and treating and converting portions of a substantially full range catalytically cracked gasoline. It is a further object of the invention to provide a process essentially comprising a specific combination of steps and conditions and applying these to subdivisions of a substantially full range catalytically cracked gasoline appropriate to said steps and conditions, that a substantially olefin-free, high-octane number gasoline is produced.

Other concepts, objects and the several advantages of this invention are apparent from a consideration of this disclosure, the drawings and the appended claims.

According to the invention, the motor octane number of a substantially full range, catalytically cracked gasoline is improved by steps combined to separate from the gasoline as a lower boiling fraction one containing olefins and a substantial, preferably predominant portion of the paraffins and isoparaffins therein, a high boiling fraction containing substantially all of the aromatics reasonably thus separated along with concomitant proportions of naphthenes, usually constituting the predominant portion of the naphthenes in the gasoline, and olefins, also usually constituting a predominant portion of the gasoline, the separation being accomplished by fractionating a gasoline into a fraction boiling substantially below a temperature of the order of about F. and a fraction boiling substantially above said temperature, the preferred temperature, in each case depending upon. the analysis of the original gasoline and the fractions desired to be obtained therefrom, according to the invention; solvent extracting the high boiling fraction to obtain a raffinate and an extract, the raffinate containing a large, predominant portion, if, indeed, not substantially all, of the parafiin s, olefins and naphthenes of said high boiling fraction and the extract containing substantially all of the aromatics and being as free from paraffins, olefins and naphthenes as desirably possible; subjecting the ralfinate together with said low boiling fraction and with added isobutane as may be desired to alkylation conditions to convert the admixture to a product high in isoparaffinic content; and combining said product, suitably, with said extract.

According to a modification of the invention, the product resulting from the alkylation operation can be and l suitably is fractionated to obtain a fraction rich in isoparaflins, usually a fraction boiling substantially below about 275 F., and a fraction boiling above 275 F., containing predominantly paraflins, naphthenes and little or no aromatics; the last fraction being aromatized by subjecting the same to, say, a vapor phase conversion operation, later described; and suitably combining the extract, the fraction boiling substantially below about 275 F. and the aromatized fraction to obtain the further improved fuel.

Thus, the invention, according to the first concept set out herein, can be applied to increase the Motor Octane Number of a catalytically cracked gasoline from, say 84.8 to 92.5 and, according to the second concept, the resulting fuel will have a Motor Octane Number of 95. Notably, also, this fuel will additionally have a substantially increased Research Octane Number, the increase being from, say, 97.5 for the original gasoline to 100 for the final fuel.

Referring now to the drawings, FIGURE 1 is a schematic flow plan of a known process for alkylating olefins in a cracked gasoline. FIGURE 2 is a schematic flow plan of an operation according to the present invention wherein the portion of the catalytically cracked gasoline boiling above approximately 175 F. is solvent extracted and the rafiinate thus obtained is combined with that portion boiling below approximately 175 F. and subjected to alkylation conditions. FIGURE 3 is a flow plan illustrating schematically that the alkylated stream of FIGURE 2 is split into a fraction rich in highly branched isoparaflins, usually boiling below about 275 F. and a fraction containing less branched to slightly branched isoparaflins, and naphthenes, usually boiling above about 275 F., the latter fraction being treated to convert parafiins and naphthenes to aromatics therein and then combining the fraction boiling below about 275 F. with the aromatic extract earlier obtained and the aromatized fraction boiling above about 275 F.

Generally, referring to the three figures of the drawing, it should be noted that FIGURES 2. and 3 differ from FIGURE 1, a prior art operation, in that FIGURES 2 and 3 provide a solvent extraction step. Further, FIG- URES 2 and 3 further differ from FIGURE 1 in that the temperature at which division of the feedstock is initially made is quite different in FIGURES 2 and 3 from that which it is in FIGURE 1. Further, in FIGURE 3 there is a division of the alkylated product with aromatization of the higher boiling fraction, as further described in connection with FIGURE 3.

Referring now to FIGURE 1, a full range catalytically cracked gasoline is passed by 1 into fractionation zone 2 wherein it is divided into stream 3, essentially high in aromatics, and stream 4, high in paraflinic and olefinic constituents. This stream is alkylated in alkylation zone 5 under known alkylating conditions, such as employing hydrofluoric acid as a catalyst at a temperature of 80120 F., and a contact time of 5-10 minutes, and a suitably high isobutane ratio (e.g., 6-15 mols per mol of olefin), to produce C containing product stream 6. This product now contains a much higher percentage of parafiinic, especially isoparaflinic, constituents and is now virtually free from olefins but contains some naphthenes and aromatics. This product is combined with stream 3 to form final product 7.

In a specific embodiment of FIGURE 1, using 100 voltimes of a full-range catalytically cracked gasoline having a Research Octane Number (RON) of 97.5 and a Motor Octane Number (MON) of 84.8, and using a cut point in fractionating column 2 of 275 F., 120 volumes of product (stream 7) are obtained having an RON of 97 and an MON of 92 (all octane numbers are with 3 ml. TEL). The olefin content is reduced from about 43 to about 8 volume percent, and the sensitivity is reduced from about 13 to about 5 units. However, it is apparent that the final product of the prior art process contains a 4 substantial amount of olefins. For reasons already recited, olefins and and will be increasingly undesirable in motor fuels.

Referring now to FIGURE 2, an operation according to the invention, the same charging stock or feedstock as used in connection with the description of FIGURE 1 is fractionated or divided into two fractionsa high boiling and a low boiling fraction, the temperature at which division is practiced being of the order of 175 F., as against the 275 F. in FIGURE 1 for the first division of the feedstock.

Thus, the feed entering by 10 into fractionation zone 11 is split into low boiling fraction 12, boiling below about 175 F., and high boiling fraction 13, boiling above about 175 F. Stream 13, which contains a high per.- centage of aromatics, is, according to the invention, subjected to solvent extraction conditions in zone 14, producing an extract containing substantially all the aromatics recovered via 16. The raflinate containing substantial paraflinic and olefinic material is combined at 17 with the fraction 12 and passed to alkylation zone 18. Stream 17 contains substantial paraflinic constituents and a combined olefinic content which is quite high. Zone 18 is operated, say, with sulfuric acid or with hydrofluoric acid as in the process of FIGURE 1, adding isobutane through line 21. The efiluent from zone 18 is passed by 19 into confluence with the extract 16 to form the final product 20.

Solvent extraction zone 14 can be operated with any desired solvent suitable for the extraction to be accomplished and the solvent can be by way of example, an alkylene glycol, preferably diethylene glycol or a diethylene glycol-triethylene glycol-water mixture.

In this embodiment of the process of the invention, 127.5 volumes of olefin-free product having an RON of 94.5 and an MON of 92.5 are obtained. Thus a higher yield of olefin-free product having only a slightly reduced Research Octane Number and having a sensitivity of only 2 units is obtained.

Referring now to FIGURE 3, both the Research and Motor Octane Number of the product of the invention can be still further increased with only a small increase in sensitivity, i.e., from about 2 to about 5 units. The numbers which have been primed in FIGURE 3 correspond to those of FIGURE 2 which are, of course, not primed. Further, referring to FIGURE 3, the alkylated product 19 is, in this figure, passed to fractionation zone 27, forming a fraction boiling substantially below about 275 F. and a fraction boiling substantially above about 275 F. The low boiling product 22 is substantially olefin free and can be used in the final fuel, as noted herein. The high boiling product is passed by 23 to aromatization zone 24 and the efiluent 25 from this zone is combined with product 22 and 16 to form at 26 113 volumes of product having an MON of and an RON of 100.

As noted, the conditions in the various zones of the invention are those which can be supplied by one skilled in the art in possession of this disclosure having studied the same.

In addition to the conditions recited above for the respective zones, the conditions in zone 24 of FIGURE 3 can be in the range of about 600 to about 1300 F. and a ratio of gaseous hydrogen fluoride to the hydrocarbon feed of about .1 to about 4, preferably .5 to about 2. The liquid hourly space velocity is maintained at from about .2 to about 4 v./v., depending upon the temperature and the acid to hydrocarbon ratio. The pressure in this zone is usually atmospheric or slightly above. With lighter feeds, temperatures can be from about 850 to about 1150 F., while somewhat lower temperatures are preferred for heavier streams. The contact mass which is employed in zone 24 is a highly porous, non-reactive agent and preferably is charcoal or activated carbon. Other contact masses, such as calcium fluoride, magnesium fluoride and other analogous compositions can be employed.

The temperatures at which division of the initial charge stock is made are not critical in the sense that some reasonable variation can be accomplished within the scope of the invention as claimed. The temperatures are given together with analysis for principal components of the streams used and to be obtained to permit one skilled in the art to select, depending upon economics of operation and the market at the time, the temperature for the division which will best suit his purposes. The processes of the invention as described in connection with FIG- URES 2 and 3 lend themselves well to some rearrangement and, accordingly, are possessed of considerable flexibility. However, one skilled in the art should understand that he will desire to consider for each feedstock the economic-s and other points involved in the operation to be set forth or scheduled. He will wish to consider the analysis of the streams used and to be obtained not only with respect to economics at the point of division but also, as he will readily understand, with respect to the results obtainable in the several ensuing steps of solvent extraction, alkylation and aromatization.

It will be evident that the starting gasoline which results from catalytic cracking is one which can be replaced in the presence of the claimed invention by equivalent material. Thus, so long as the starting material possesses a general overall chemical composition equivalent to the gasoline herein identified for illustrative purposes, it will be a feed suited for the operation claimed. Such gasoline can be blended from several gasolines or other fractions of material containing one or more components rendering these desirable in the feed. Those familiar with the chemical nature of gasoline here contemplated as .feedstocks will know that these contain usually as principal hydrocarbons the following:

Liquid volume percent Paraffins -30 Olefins 40-50 Naphthenes 5-15 Aromatics 15-30 Usually somewhat more than half the paraffins are normal paraffins. The boiling range of the feedstock is usually about 50 F. to about 450 F.

Depending upon the aromatic content and the specific material of the aromatic in the gasoline, the low and high boiling fractions contemplated in the invention and into which the fed is divided will be so formed that all aromatics it is reasonable to avoid having in the low boiling fraction later to be passed to the alkylation zone Will be in the high boiling or higher boiling fraction, depending upon the number of fractions into which the gasoline is divided, i.e., the concept of the invention includes so arranging the operation that the stream or streams passed to solvent extraction will desirably contain the aromatics as far as is reasonably possible.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, drawings and the appended claims to the invention the essence of which is that a catalytically cracked gasoline is converted to a product having high motor octane number and containing virtually no olefin constituents by separating said gasoline into fractions, one of them preeminently suited to alkylation and the other to solvent extraction, the fraction suitable for alkylation is alkylated in the presence of the raffinate obtained from the solvent extraction, whereupon the alkylated product is combined with the extract of the solvent extraction according to one concept of the invention and, in another concept of the invention, the alkylated product is separated into a fraction suited for ultimate use, while another fraction obtained from it is aromatized to render it suitable for ultimate use, the last said fraction being combined with the extract from the solvent extraction to form a final product having a still higher motor octane number and being also olefin free.

I claim:

1. A process for improving a substantially full range catalytically cracked gasoline comprising among hydrocarbons contained therein olefins and aromatics by reducing substantially entirely its olefin content which comprises:

(A) fractionating said gasoline into at least two fractions (1) a low boiling fraction including therein a substantial portion of the gasoline and having a boiling point range substantially below about F. (2) a high boiling fraction including therein a large proportion of said aromatics and having a boiling range substantially above about 175 F. (B) subjecting the high boiling fraction to solvent extraction conditions to form at least two fractions (1) a rafiinate fraction, and (2) an extract containing substantially all aromatics of said high boiling fraction reasonably recoverable in said solvent extraction, said extract being substantially free from olefin (C) subjecting said low boiling fraction together with said raflinate to alkylation conditions in presence of added isoparafiin forming an alkylated product substantially free from olefin, and

(D) combining said extract and said alkylated product to form said gasoline.

2. A process according to claim 1 wherein the alkylated product is (A) fractionated to form at least two fractions (1) a low boiling fraction having a relatively high octane number, and

(2) a high boiling fraction having a relatively low octane number (B) subjecting said high boiling fraction to aromatization conditions, forming an aromatics containing stream substantially free from olefin, and

(C) combining said low boiling fraction, said aromatics containing stream and said extract to form said improved gasoline.

3. A process according to claim 1 wherein the alkylated product is formed in an alkylation zone employing a catalyst selected from hydrofluoric and sulfuric acids.

4. A process according to claim 2 wherein the low boiling fraction of said claim has a boiling range substantially below about 275 F. and the high boiling fraction of said claim has a boiling range above about 275 F.

5. A process according to claim 2 wherein the high boiling fraction is subjected to vapor phase aromatization conditions in the presence of a contact agent.

6. A process according to claim 5 wherein low boiling fraction of claim 2, the aromatized fraction of claim 5 and the extract of claim 2 are combined to form said improved gasoline.

7. A process according to claim 2 wherein the high boiling fraction is subject to the vapor phase aromatization conditions in the presence of a contact agent consisting essentially of activated carbon or charcoal.

References Cited UNITED STATES PATENTS 2,387,309 10/1945 Sweeney 260-68349 2,982,716 5/1961 Findlay 260-68349 3,023,157 2/1962 Ellert et a1. 208-93 2,439,600 4/ 1948 Goldsby et a1. 208-70 3,138,645 6/1964 Hutchings 260-68362 3,211,803 10/1965 Chapman 20887 DELBERT E. GANTZ, Primary Examiner.

H. LEVINE, Assistant Examiner. 

